Description: The
entire carapace is hard (calcified)
on this hermit crab. The walking legs are quite long for
hermit crabs.
Color is brownish or pink with a reddish iridescent sheen.
Carapace
width to 2.8 cm.

How to Distinguish
from
Similar Species: The
fully calcified carapace with dorsal spines, with the long legs and
iridescent
sheen make this species stand out.

Geographical
Range: Arctic
Ocean to Puget
Sound

Depth Range: 3-412
m depth

Habitat: Open
mud or sand bottoms

Biology/Natural
History:_Often
carries a
shell barely large enough for its abdomen. Often has stinging
hydroids
on its shell.

This photo is of a female carrying eggs, who abandoned her shell in
the seawater tank. Photo by Dave Cowles, July 2005

A closeup of the head and shield of Labidochirus splendescens.
Photo by Dave Cowles, July 2005

On a beam trawl in San Juan
Channel,
100-120 m deep, in
July 2007 we found several Labidochirus splendescens
living in shell-like
formations that appeared to be composed entirely of the Hydroid Hydractinia
sp. Hydractinia
is known to frequently live on shells inhabited by hermit crabs, and to
sometimes overgrow the shell. In these cases the hydroid has
so completely
overgrown the tiny shell that the shell can no longer be seen (but see
the X-ray images). This shows that the hydroid is capable of
a great
deal of gastropod-like spiral growth around the hermit crab on its
own.
Digital X-rays compliments of Julie Kellogg, DDS and the Tietan Dental
Clinic in Walla Walla.

Two different Labidochirus
were
living in Hydractinia.
The smallest Hydractinia was about 1.3 cm long and
the largest was
about 2.5 cm long. The dark marks on these Hydractinia
are
an artifact of removing the crabs from the shells.

Here is a view of the "aperture" of the smaller Hydractinia,
seen on the left in the photo at left..
The hydroid is coiled
like a snail but no hard snail shell can be felt even in the "spire" on
the left side.

Here is the larger Hydractinia,
seen at right in the photo at left. The outer "whorl" of the
hydroid
flares more widely than normally seen in a gastropod. No hard
snail
shell can be felt even in the "spire" on the left side.

This X-ray of the Hydractinia
"house" above shows that the posterior half of the "house" is composed
of a fragmented gastropod shell, while the front of the "house" is
entirely Hydractinia.
The shadowy outline is the edge of the Hydractinia
colony.

This X-ray of the Hydractinia
"house" above shows a similar arrangement, except that the fragmented
shell
makes up only a third or less of the "house". In some
symbioses the
Cnidarian is said to slowly dissolve the shell but this shell looks
more
fragmented than dissolved. I am guessing that it was
fragmented when
the hermit crab initially took up residence. If that is the
case,
the Hydractinia
has made
this shell a vastly superior dwelling than it initially was.

Here is a closeup of the texture of the outside
of the
hydroid colony.
The hydroid polyps are gone but the hydrotheca remains. This
hydroid
was not studied until several days after the crab was removed so I do
not
know if the hydroid was living when collected.

A view inside the "aperture" of the larger
hydroid
shows the smooth
inner surface which would have contacted the body of the hermit crab.

A view of the edge of the "aperture" of the
larger
hydroid shows that
the "house" is composed entirely of hydroid at least along the
edge--there
is no trace of a calcified shell.

Another example of Labidochirus
splendescens in a shell covered withHydractinia.
The Hydractinia
has grown well past the original margins of this shell as well to form
an enlarged, shell-like case for the hermit crab to live in.
Photo by Dave Cowles, July 2016Authors and Editors of Page:
Dave Cowles (2005): Created original page